Enhanced photocatalytic hydrogen evolution of Ru/TiO2-x via oxygen vacancy-assisted hydrogen spillover process.

Hydrogen spillover effects will significantly improve the activity of photocatalytic hydrogen evolution reactions (HER), while their introduction and optimization require the construction of an excellent metal/support structure. In this study, we have synthesized Ru/TiO2-x catalysts with controlled oxygen vacancy (OVs) concentrations using a simple one-pot solvothermal method. The results show that Ru/TiO2-x3 with the optimal OVs concentration exhibits an unprecedentedly high H2 evolution rate of 13604 µmol·g-1·h-1, which was 45.7 and 2.2 times higher than that of TiO2-x (298 µmol·g-1·h-1) and Ru/TiO2 (6081 µmol·g-1·h-1). Controlled experiments, detailed characterizations, and theoretical calculations have revealed that the introduction of OVs on the carrier contributes to the hydrogen spillover effect in the metal/support system photocatalyst and that the process of hydrogen spillover in this system can be optimized by modulating the OVs concentration. This study proposes a strategy to decrease the energy barrier of hydrogen spillover and enhance photocatalytic HER activity. Moreover, it investigates the effect of OVs concentration on the hydrogen spillover effect in the photocatalytic metal/supports system.

Dual step-scheme heterojunction with full-visible-light-harvesting towards synergistic persulfate activation for enhanced photodegradation.

The occurrence of micropollutants in aquatic media raises great concern because of their biological toxicity and persistence. Herein, visible-light-driven photocatalyst titanium dioxide/graphitic carbon nitride/triiron tetraoxide (TiO2-x/g-C3N4/Fe3O4, TCNF) with oxygen vacancies (Ov) was prepared via a facile hydrothermal-calcination method. The complementary visible-light co-absorption among semiconductors enhances light-harvesting efficiency. The built-in electric field formed during Fermi level alignment drives photoinduced electron transfer to improve charge separation across the interfaces. The increased light-harvesting and favorable energy band bending significantly enhance the photocatalytic performance. Therefore, TCNF-5-500/persulfate system could effectively photodegrade bis-phenol A within 20 min under visible-light irradiation. Moreover, the superior durability, non-selective oxidation, adaptability, and eco-friendliness of the system were confirmed by different reaction conditions and biotoxicity assessment. Furthermore, the photodegradation reaction mechanism was presented according to the major reactive oxygen species produced in the system. Thus, this study constructed a dual step-scheme heterojunction by tuning visible-light absorption and energy band structure to increase the charge transfer efficiency and photogenerated carrier lifetime, which has great potential for environmental remediation using visible photocatalysis.

Tumor-microenvironment activated duplex genome-editing nanoprodrug for sensitized near-infrared titania phototherapy.

Near-infrared (NIR)-light-triggered nanomedicine, including photodynamic therapy (PDT) and photothermal therapy (PTT), is growing an attractive approach for cancer therapy due to its high spatiotemporal controllability and minimal invasion, but the tumor eradication is limited by the intrinsic anti-stress response of tumor cells. Herein, we fabricate a tumor-microenvironment responsive CRISPR nanoplatform based on oxygen-deficient titania (TiO2-x ) for mild NIR-phototherapy. In tumor microenvironment, the overexpressed hyaluronidase (HAase) and glutathione (GSH) can readily destroy hyaluronic acid (HA) and disulfide bond and releases the Cas9/sgRNA from TiO2-x to target the stress alleviating regulators, i.e., nuclear factor E2-related factor 2 (NRF2) and heat shock protein 90α (HSP90α), thereby reducing the stress tolerance of tumor cells. Under subsequent NIR light illumination, the TiO2-x demonstrates a higher anticancer effect both in vitro and in vivo. This strategy not only provides a promising modality to kills cancer cells in a minimal side-effects manner by interrupting anti-stress pathways but also proposes a general approach to achieve controllable gene editing in tumor region without unwanted genetic mutation in normal environments.

Dual pH-/Photo-Responsive Color Switching Systems for Dynamic Rewritable Paper.

Smart color switching materials that can change color with a fast response and a high reversibility have attracted increasing attention in color-on-demand applications. However, most of them can only respond to a single stimulus from their external environment, which dramatically limits their broad applications. To address this problem, we report a new strategy in developing a dual pH-/photo-responsive color switching system by coupling the pH-dependent and redox-driven color switchable neutral red (NR) with photoreductive TiO2-x nanoparticles. The biodegradable TiO2-x nanoparticles/NR/agarose gel film shows a rapid color switching between yellow and red upon stimulation with acidic/basic vapors in more than 20 cycles because of the protonation and deprotonation process of NR. Moreover, the film shows interesting photoreversible color switching properties under both acidic and basic conditions, including a fast response time and a high reversibility. Taking advantage of the excellent dual pH-/photo-responsive color switching properties, we demonstrated the potential applications of the TiO2-x nanoparticles/NR/agarose gel film in dynamic rewritable paper, in which the created patterns by photo-printing produce dynamic color changing upon applying an acidic or a basic vapor. We believe that the result will enable a new path for the development of dual- and even multi-responsive color switching systems, broadening their new applications.

Rational design of all-solid-state TiO2-x/Cu/ZnO Z-scheme heterojunction via ALD-assistance for enhanced photocatalytic activity.

Poor visible light utilization and charge separation efficiency of TiO2 restrict its extensive application in the photocatalytic field. Herein, a specific Z-scheme TiO2-x/Cu/ZnO heterojunction was successfully constructed by atomic layer deposition (ALD) technique and spray pyrolysis technology. Benefited from the surface plasmon resonance (SPR) effect of Cu and Z-scheme heterojunction, the visible light absorption capacity was greatly enhanced. Meanwhile, ZnO nanolayer coating, prepared by ALD technique, protects Cu element to hinder its oxidation, thus enhancing the separation efficiency of photogenerated carriers. Therefore, the photocatalytic hydrogen production performance was significant improved, exhibiting a maximum value of 342.0 µmol·g-1·h-1 for the optimal B-T-0.1C-10Z (black TiO2/0.1Cu/10 nm ZnO) sample without any noble-metal cocatalyst, which is higher than pure TiO2 (310.7 µmol·g-1·h-1, with 3 wt% Pt) synthesized by spray pyrolysis method under equal conditions. In addition, a possible mechanism for the enhanced performance was briefly discussed based on the experimental results.

Non-noble metal plasmonic enhanced photoelectrochemical sensing of chlorpyrifos based on 1D TiO2-x/3D nitrogen-doped graphene hydrogel heterostructure.

Low-cost and resource-rich non-noble metal plasmonic materials have attracted tremendous attention as potential substitutes for plasmonic noble metals. Herein, 3D nitrogen-doped graphene hydrogels (NGH) decorated with Ti3+ self-doped 1D rod-shaped titanium dioxide nanorods (TiO2-x NR), 10-25 nm in size, were prepared by a facile one-step method. It was found that the as-fabricated TiO2-x NR/NGH showed a synergistic effect, displaying enhanced photoelectrochemical (PEC) activity by controlling the nanoscale architecture and improving the electronic properties, while also producing abundant oxygen vacancies, which extended the light harvesting and suppressed the recombination of electron-hole pairs induced by the non-noble metal surface plasmon resonance (SPR) effect. In particular, the transient-state photocurrent intensity of the TiO2-x NR/NGH composites was 5.1 times as high as that of pure TiO2. Therefore, the TiO2-x NR/NGH composites could serve as a substrate material for PEC sensing, providing a good basis for selective and sensitive detection of chlorpyrifos. Under optimal conditions, the constructed PEC sensor was found to have several advantages including a broad linear range (0.05 ng/mL-0.5 µg/mL), low detection limit (0.017 ng/mL), and considerable stability, demonstrating that the sensor may offer a promising route in the field of environmental analysis.

One-step synthesis of black TiO2-x microspheres by ultrasonic spray pyrolysis process and their visible-light-driven photocatalytic activities.

Black TiO2-x has recently emerged as one of the most promising visible-light-driven photocatalysts, but current synthesis routes that require a reduction step are not compatible with cost-effective mass production and a relatively large particle such as microspheres. Herein, we demonstrate a simple, fast, cost-effective and scalable one-step process based on an ultrasonic spray pyrolysis for the synthesis of black TiO2-x microspheres. The process utilizes an oxygen-deficient environment during the pyrolysis of titanium precursors to directly introduce oxygen vacancies into synthesized TiO2 products, and thus a reduction step is not required. Droplets of a titanium precursor solution were generated by ultrasound energy and dragged with continuous N2 flow into a furnace for the decomposition of the precursor and crystallization to TiO2 and through such a process spherical black TiO2-x microspheres were obtained at 900 °C. The synthesized black TiO2-x microsphere with trivalent titanium/oxygen vacancy clearly showed the variation of physicochemical properties compared with those of white TiO2. In addition, the synthesized microspheres presented the superior photocatalytic activity for degradation of methylene blue under visible light irradiation. This work presents a new methodology for a simple one-step synthesis of black metal oxides microspheres with oxygen vacancies for visible-light-driven photocatalysts with a higher efficiency.

Efficient Photocatalytic Hydrogen Evolution over TiO2-X Mesoporous Spheres-ZnO Nanorods Heterojunction.

Photocatalytic water splitting into hydrogen is regarded as one of the key solutions to the deterioration of the global environment and energy. Due to the significantly reduced grain boundaries, ZnO nanorods facilitate a fast electron transfer through their smooth tunnels and are well suited as a photocatalyst. However, the photocatalytic hydrogen evolution performance of pristine ZnO nanorods is still low due to the high recombination rate of photogenerated electron-hole pairs and the less light absorption. Here, a novel structure about black ZnO nanorods (NRs)/TiO2-X mesoporous spheres (MSs) heterojunction has been prepared and the photocatalytic hydrogen evolution performance has been explored. The photocatalytic activity test results showed that ZnO NRs/TiO2-X MSs exhibited higher catalytic activity than ZnO NRs for hydrogen production. Compared to the pure ZnO NRs photoanode, the photocurrent of ZnO NRs/TiO2-X MSs heterojunction photoanode could reach 0.41 mA/cm2 in view of the expanding spectral response region and effective inhibition of e-/h+ recombination at the same condition. Using a relatively integrated experimental investigation and mechanism analysis, we scrutinized that after being treated with NaBH4, TiO2 MSs introduce oxygen vacancies expanding the photocatalytic activity of pure TiO2, and improving conductivity and charge transport capabilities through coating on ZnO NRs. More importantly, the results provide a promising approach in the NRs/MSs composite structure serving as photoanodes for photocatalytic hydrogen production.

Plasmonic Oxygen-Deficient TiO2-x Nanocrystals for Dual-Band Electrochromic Smart Windows with Efficient Energy Recycling.

Dual-band electrochromic smart windows capable of the spectrally selective modulation of visible (VIS) light and near-infrared (NIR) can regulate solar light and solar heat transmittance to reduce the building energy consumption. The development of these windows is however limited by the number of available dual-band electrochromic materials. Here, plasmonic oxygen-deficient TiO2-x nanocrystals (NCs) are discovered to be an effective single-component dual-band electrochromic material, and that oxygen-vacancy creation is more effective than aliovalent substitutional doping to introduce dual-band properties to TiO2 NCs. Oxygen vacancies not only confer good near-infrared (NIR)-selective modulation, but also improve the Li+ diffusion in the TiO2-x host, circumventing the disadvantage of aliovalent substitutional doping with ion diffusion. Consequently optimized TiO2-x NC films are able to modulate the NIR and visible light transmittance independently and effectively in three distinct modes with high optical modulation (95.5% at 633 nm and 90.5% at 1200 nm), fast switching speed, high bistability, and long cycle life. An impressive dual-band electrochromic performance is also demonstrated in prototype devices. The use of TiO2-x NCs enables the assembled windows to recycle a large fraction of energy consumed in the coloration process ("energy recycling") to reduce the energy consumption in a round-trip electrochromic operation.

Honeycombed Au@C-TiO2-Xcatalysts for enhanced photocatalytic mineralization of Acid red 3R under visible light.

The mineralization of organic pollutants under visible light is challenging, limiting the practical application of photocatalytic technology in wastewater treatment. To achieve the efficient mineralization of Acid red 3R (AR3R), a series of honeycombed catalysts (TiO2, C-TiO2-X, Au@TiO2 and Au@C-TiO2-X) were prepared via a facile in situ synthetic method and characterized by XRD, TEM, BET, XPS and DRS, respectively. The introduction of C and Au species promote the simultaneous generation of •O2- and •OH over Au@C-TiO2-X under visible light radiation. The Au@C-TiO2-X catalyst showed superior performance for the deep mineralization of AR3R, affording a TOC removal rate larger than 90 % within 240 min under visible light (> 420 nm). The photocatalytic degradation mechanism of AR3R is proposed according to UV-vis and in situ DRIFTS analysis. The superior photocatalytic activity of Au@C-TiO2-X is attributed to the synergistic effect of •O2- and •OH owing to C doping and Au deposition.

TiO2-x/TiO2-Structure Based 'Self-Heated' Sensor for the Determination of Some Reducing Gases.

In this research we report the gas-sensing properties of TiO2-x/TiO2-based hetero-structure, which was 'self-heated' by current that at constant potential passed through the structure. Amperometric measurements were applied for the evaluation of sensor response towards ethanol, methanol, n-propanol and acetone gases/vapours. The sensitivity towards these gases was based on electrical resistance changes, which were determined by amperometric measurements of current at fixed voltage applied between Pt-based contacts/electrodes deposited on the TiO2-x/TiO2-based layer. X-ray diffraction (XRD) analysis revealed the formation of TiO2-x/TiO2-based hetero-structure, which is mainly based on Ti3O5/TiO2 formed during the hydro-thermal oxidation-based sensing-layer preparation process. Additionally, photoluminescence and time-resolved photoluminescence decay kinetics-based signals of this sensing structure revealed the presence of TiO2 mainly in the anatase phase in the TiO2-x/TiO2-based hetero-structure, which was formed at 400 °C annealing temperature. The evaluation of TiO2-x/TiO2-based gas-sensing layer was performed at several different temperatures (25 °C, 72 °C, 150 °C, 180 °C) and at these temperatures different sensitivity to the aforementioned gaseous materials was determined.

Hierarchical TiO2-x nanoarchitectures on Ti foils as binder-free anodes for hybrid Li-ion capacitors.

Hybrid Li-ion capacitor (LIC) draws more attention as novel energy storage device owing to its high power density and high energy density. Designing three-dimensional electrode materials is beneficial for improving electrochemical performance of LICs. Herein, an improved hydrothermal method combined with an ion-exchange reaction is used to manufacture oxygen vacancies (OVs)-doping TiO2 (TiO2-x) nanowires/nanosheets (NWS) on Ti-foil. Then TiCl4 treatment is performed to form TiO2-x NWS/nanocrystallines (NWSC). These-obtained hierarchical nanoarchitectures assumes enrich electro-active sites and contact areas, which can improve electron transference and structural stability. The TiO2-x NWSC is used as binder-free anode for Li-ion battery and achieves high specific capacity (300 mAh g-1 at 0.1 A g-1), excellent rate capability (102 mAh g-1 at 5 A g-1) and long cycle stability (44% after 1000 cycles at 1 A g-1). LICs assembled with a TiO2-x NWSC anode and an activated carbon cathode have an energy density of 44.2 W h kg-1 at the power density of 150 W kg-1. Therefore, the TiO2-x NWSC is a potential candidate for high energy and high power electrochemical energy storage devices.

Enhanced visible-light activation of persulfate by Ti3+ self-doped TiO2/graphene nanocomposite for the rapid and efficient degradation of micropollutants in water.

In this study, a novel TiO2-x/rGO-PS-Vis process was developed, which utilizes the TiO2-x/rGO (Ti3+ and oxygen vacancies self-doped TiO2 coupled with reduced graphene oxide) nanocomposite as a promising and efficient activator of persulfate (PS) for the enhanced oxidation of micropollutants under visible -light irradiation. TiO2-x/rGO exhibited a significantly high activity for PS activation to produce more sulfate radicals (SO4-) and hydroxyl radicals (OH). Therefore, almost 100% BPA (10 mg/L) and 80% TOC can be removed just within 12 min with 1.0 g/L TiO2-x/rGO and 2 mM PS under visible light. Moreover, it was found that many other typical micropollutants, such as phenol, acetaminophen and sulfamethoxazole can also be effectively degraded by this process. Electron paramagnetic resonance (EPR) and radical quenching experiments indicated that both SO4- and OH contribute to the degradation of organics, and the radical process was the main degradation pathway. In addition, the effects of PS concentration, catalyst dosage, initial solution pH and inorganic anions were investigated systematically. Experiments carried out in the real background of water matrix with low-concentration of BPA indicated that the proposed TiO2-x/rGO-PS-Vis process has strong non-selective photo-oxidative ability for the removal of micropollutants in water.

Electric charging/discharging characteristics of super capacitor, using de-alloying and anodic oxidized Ti-Ni-Si amorphous alloy ribbons.

Charging/discharging behaviors of de-alloyed and anodic oxidized Ti-Ni-Si amorphous alloy ribbons were measured as a function of current between 10 pA and 100 mA, using galvanostatic charge/discharging method. In sharp contrast to conventional electric double layer capacitor (EDLC), discharging behaviors for voltage under constant currents of 1, 10 and 100 mA after 1.8 ks charging at 100 mA show parabolic decrease, demonstrating direct electric storage without solvents. The supercapacitors, devices that store electric charge on their amorphous TiO2-x surfaces that contain many 70-nm sized cavities, show the Ragone plot which locates at lower energy density region near the 2nd cells, and RC constant of 800 s (at 1 mHz), which is 157,000 times larger than that (5 ms) in EDLC.